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Wilkinson鈥檚 catalyst, formally chloridotris(triphenylphosphine)rhodium(I) [RhCl(PPh3)3], is a coordination complex that catalyzes a wide range of organic reactions, principally the hydrogenation of alkenes and alkynes and hydrofunctionalization reactions across double bonds such as hydroacylation (hydroformylation) and hydrosilylation. It is named for Geoffrey Wilkinson, who won the 1973 Nobel Prize in Chemistry.
Wilkinson, at Imperial College London, published his first papers on rhodium catalysts in 1965. At the Robert A. Welch Foundation Conference on Chemical Research that year, he described the synthesis of the complex, in which rhodium(III) chloride1 (RhCl3) and excess triphenylphosphine2 (PPh3) are heated in ethanol solution. In a second paper, with three coauthors, he elucidated the formed when RhCl(PPh3)3 catalyzes hydrogenation reactions of unsaturated compounds.
Three years later, Wilkinson, along with D. Evans and J. A. Osborn, described the use of rhodium complex catalysts, including RhCl(PPh3)3, to promote the . Overall, Wilkinson and his colleagues wrote 26 papers from 1965 to 1990 on the synthesis, properties, and catalytic behavior of RhCl(PPh3)3 and related complexes.
1. CAS Reg. No. 10049-07-7.
2. CAS Reg. No. 603-35-0.
Wilkinson鈥檚 catalyst hazard information*
| Hazard class** | GHS code and hazard statement | |
|---|---|---|
| Skin corrosion/irritation, category 2 | H315鈥擟auses skin irritation |  |
| Skin sensitization, category 1 | H317鈥擬ay cause an allergic skin reaction | |
Serious eye damage/eye irritation, category 2A | H319鈥擟auses serious eye irritation | |
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335鈥擬ay cause respiratory irritation | |
| Long-term (chronic) aquatic hazard, category 4 | H413鈥擬ay cause long-lasting harmful effects to aquatic life | |
*Compilation of multiple safety data sheets.
**Globally Harmonized System (GHS) of Classification and Labeling of Chemicals.听.
Molecule of the Future
Varespladib1 is a medication that was originally developed by Anthera Pharmaceuticals (Hayward, CA) as a treatment for inflammatory diseases such as acute coronary syndrome and acute chest syndrome. A Phase 3 clinical trial, however, showed inadequate efficacy, and Anthera halted the trial in 2012.
A few years later, varespladib gained a new lease on life. As the Los Angeles Times reported last month, for several years Matthew Lewin at the California Academy of Sciences (San Francisco) had tried to develop an oral medication to administer quickly to individuals bitten by poisonous snakes. Learning that varespladib blocks phospholipase A22, a toxic enzyme that exists in almost all snake venoms, he formulated it into a pill that (e.g., neurological damage and severe听 bleeding) if given immediately after the snakebite.
In 2021, Lewin, then at newly formed company Ophirex (Corte Madera, CA), with colleagues there and in Australia and Bangladesh reported that varespladib of venoms from several species of African spitting cobra in the genus Naja.
1. CAS Reg. No. 172732-68-2.
2. CAS Reg. No. 9001-84-7.
Molecule in the News
Hydrogen cyanide1 (HCN) was the molecule of the week for December 6, 2010. It is, of course, a poisonous gas; but it has many industrial uses.
Last month, HCN was in the news for a quite different reason. Jonah S. Peter*, Tom A. Nordheim, and Kevin P. Hand at Caltech鈥檚 Jet Propulsion Laboratory (La Ca帽ada Flintridge, CA) reported that the Cassini spacecraft observed HCN, among many other molecules, in plumes ejected from the south pole of Saturn鈥檚 moon Enceladus. The authors speculate that on the moon.
1. CAS Reg. No. 74-90-8.
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fast facts
| CAS Reg. No. | 14694-95-2 |
| SciFinder nomenclature | Rhodium, chlorotris (triphenylphosphine)-, (SP-4-2)- |
| Empirical formula | C54H45ClP3Rh |
| Molar mass | 925.22 g/mol |
| Appearance | Reda crystals or powder |
| Melting range | 245鈥�250 掳C |
| Water solubility | Insoluble |
a. May also be red-brown or -yellow.
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